One example of a conventional thermal print head is disclosed in JP2017-65021A. The thermal print head of the above document includes a main substrate on which a wiring layer and a resistor layer are formed, and a sub-substrate on which a plurality of driver ICs are mounted. The resistor layer includes a plurality of heat generators arranged in a main scanning direction.
In printing by the above thermal print head, a printing sheet is pressed against the heat generators by a platen roller. The relative position of the platen roller and the heat generators in a sub-scanning direction is appropriately set, for example, during the manufacturing process. However, if the platen roller deviates from the set position for some reason, problems may occur such as degradation in printing quality.
In the above thermal print head, the main substrate and the sub-substrate are adjacently arranged in the sub-scanning direction, and are connected to each other with a plurality of wires. These wires and the driver ICs are covered with a protective resin. In order to avoid interference between the platen roller and the protective resin during printing, the bonding portions of the wires at the main substrate need to be kept away from the heat generators. However, this leads to an increase of the length of the main substrate in the sub-scanning direction, hindering the downsizing of the main substrate (and thus the thermal print head as a whole).